feat: add completion for fish

src/base.ts

@@ -8,7 +8,7 @@ export abstract class CompletionBase extends Command {
       char: 's',
       env: 'SHELL',
       parse: (shell) => basename(shell),
-      options: ['bash', 'zsh'],
+      options: ['bash', 'fish', 'zsh'],
       required: true,
     }),
   }

src/commands/completion/generate.ts

@@ -1,5 +1,6 @@
 import { CompletionBase } from '../../base'
 import { generateCompletionScriptForBash } from '../../utils/bash'
+import { generateCompletionScriptForFish } from '../../utils/fish'
 import { generateCompletionScriptForZsh } from '../../utils/zsh'
 
 export default class CompletionGenerate extends CompletionBase {
@@ -23,6 +24,10 @@ export default class CompletionGenerate extends CompletionBase {
       scriptContent = generateCompletionScriptForBash(this.config)
     }
 
+    if (shell === 'fish') {
+      scriptContent = generateCompletionScriptForFish(this.config)
+    }
+
     if (shell === 'zsh') {
       scriptContent = generateCompletionScriptForZsh(this.config)
     }

src/utils/fish.ts

@@ -0,0 +1,59 @@
+import type { Command } from '@oclif/command'
+import { getFirstLine } from './template'
+
+export function generateCompletionScriptForFish({
+  bin,
+  commands,
+}: Command['config']) {
+  const scriptParts: string[] = []
+
+  scriptParts.push(`set -l seen __fish_seen_subcommand_from`)
+
+  scriptParts.push(
+    `set -l commands ${commands.map((command) => command.id).join(' ')}`
+  )
+
+  for (const command of commands) {
+    if (command.hidden) {
+      continue
+    }
+
+    const commandParts: string[] = []
+
+    commandParts.push(
+      `complete -c ${bin} -n "not $seen $commands" -f -a ${
+        command.id
+      } -d '${getFirstLine(command.description)}'`
+    )
+
+    for (const [name, flag] of Object.entries(command.flags)) {
+      if (flag.hidden) {
+        continue
+      }
+
+      let flagPart = `complete -c ${bin} -n "$seen ${command.id}" -l ${name}`
+
+      if (flag.char) {
+        flagPart += ` -s ${flag.char}`
+      }
+
+      if (flag.type === 'option') {
+        if (flag.options) {
+          flagPart += ` -x -a "${flag.options.join(' ')}"`
+        } else {
+          flagPart += ` -r`
+        }
+      }
+
+      if (flag.description) {
+        flagPart += ` -d "${getFirstLine(flag.description)}"`
+      }
+
+      commandParts.push(flagPart)
+    }
+
+    scriptParts.push(commandParts.join('\n'))
+  }
+
+  return scriptParts.join('\n'.repeat(2))
+}

src/utils/template.ts

@@ -23,3 +23,7 @@ export function template(
     return parts.join('')
   }
 }
+
+export const getFirstLine = (string = ''): string => {
+  return string.split('\n')[0]
+}